Study on the properties of non-solidified materials and intelligent hole sealing device for gas drainage drilling

In order to solve the problem of the inability of solid sealing materials to block secondary fractures in the existing gas drilling plugging technology， which leads to a sharp decline of the drainage effect at the later stage of drainage， this paper proposes a simple operation method， with low cost and improved sealing effect of the gas drilling sealing.That is， a kind of non-solidified semi-fluid sealing material is injected into the confined space formed by two-stage expansion sealing material by grouting pump with pressure to seal the coal rock fractures.Meanwhile， in order to meet the demand of long-term pressure maintaining of non-solidified slurry， an intelligently controlled system of non-solidified constant pressure slurry sealing for gas drainage drilling is developed.This system can automatically monitor the gas sealing and drainage status of gas drainage，which can reduce the drilling pressure to a certain level.After the value is automatically replenished， a dynamic continuous plugging mechanism is formed.The components of the developed non-solidified materials are mainly introduced， which mainly composes of sodium-based bentonite and kaolin， and fly ash， sodium tripolyphosphate and portland cement materials are also added.By testing the changes of fluidity and water separation rate of the slurry with different water-cement ratio ranging from 5 ∶1 to 20 ∶1， the water cement ratio of four groups of non-solidified material slurry meeting the requirements were obtained， which were 8 ∶1， 10 ∶1， 12 ∶1 and 14 ∶1 respectively.Finally， by testing the retention percentage of these four groups of water-cement ratio slurry in the yarn net， the optimal water-cement ratio of non-solidified material used underground was determined to be 10 ∶1.At the same time， the intelligent gas sealing system is also introduced.The application results in the suburban coal mines show that the gas drainage concentration of the borehole is 62% higher than that of the original cement-based material， and the extraction time is two times longer.It was proved that this technology has a good application prospect.